Apparatus for cleaning the edges of wafers

ABSTRACT

The invention concerns an apparatus for cleaning the edge of a wafer that may be relatively simply constructed with low cost, and prevent the wafer from being re-contaminated by the edge cleaning, thus resulting in increase of the yield rate of wafers. The apparatus includes a cleaning agent ejection nozzle body provided on a side part of a chuck for ejecting a particulate cleaning agent (CO 2  particles) towards the side and the edge portions of the wafer held and rotated by the chuck, and a nozzle body carriage for moving the nozzle body between rest and cleaning positions.

TECHNICAL FIELD

[0001] The present invention concerns an apparatus for cleaning wafers,and more particularly an apparatus for cleaning the edges and sides ofwafers by applying solid fine volatile particles such as dry ice.

BACKGROUND ART

[0002] The process for fabricating a semiconductor device employs anapparatus for cleaning a semiconductor wafer (hereinafter referred tosimply as wafer) on whose surface is provided a thin film circuitpattern.

[0003] A conventional apparatus for cleaning a wafer is illustrated inFIG. 1. The apparatus includes a spin chuck 10 for substantiallyhorizontally supporting a wafer (W) by suction and rotating it, and atreatment liquid supply nozzle 30 arranged above the rotational centerof the spin chuck to supply a cleaning or treatment liquid on thesurface of the wafer (W).

[0004] Firstly, a motor not shown drives the spin chuck 20 to rotate thewafer (W) at a given speed. When the rotation is stabilized, thecleaning or treatment liquid is ejected from the nozzle 30 on thesurface of the wafer (W) at a given speed to clean or treat it.

[0005] If the wafer (W) has both front and back surfaces useful, thewafer (W) is reversed by a reversing mechanism to clean or treat theback surface through the same process after the front surface has beencleaned or treated.

[0006] However, although cleaning both front and back surfaces of awafer, such conventional cleaning apparatus is so designed to make itdifficult to clean the edge of a wafer. As the size of a wafer isincreased, it becomes more important to remove polymeric residualpresent in its edge, and there has been conventionally proposed aprocess of cleaning the edge employing a belt, brush, etc.

[0007] One of the processes of cleaning the edge of a wafer employing abrush is proposed in U.S. Pat. No. 5,976,267 granted to Timothy, et al.

[0008] This patent, as shown in FIGS. 2A to 2C, a wafer 250 is cleanedby the upper brush 202 moving through a scrubber in the directionindicated by an arrow 701. The lower brush 302 is arranged beneath thewafer 250 directly opposed to the upper brush 202. The upper and lowerbrushes 202 and 302 are provided with motors to rotate them as well asedge brushes 220 and 320. Two rolls 501 and 502 are provided contactingthe side of the wafer at two positions so as to rotate the wafercounterclockwise as indicated by an arrow 702. The rolls 501 and 502 arerotated respectively by stepper motors 503 and 504. The wafer 250 hasall its surfaces including the edge cleaned while rotating between thebrushes 202, 302, 220 and 320.

[0009] Removal of contaminating particles may be facilitated by a waterejector 380 arranged so as to eject water in or near a contact positionbetween the edge brushes 220 and 320 and the wafer, as shown in FIG. 2C.Such a water ejector may be positioned so as to make water flow from aplane aligned with the rotational shaft of the wafer to contact theregions between the wafer and the side scrubbing mechanism. In thiscase, water may simply move away the particles detached from the waferby the side scrubbing mechanism, or if having a pressure sufficientlylarge, directly remove the particles from the wafer. The water ejectormay be arranged in a proper place by means of a conventional supportstructure, and is positioned directly above the wafer in the drawings.The water ejector has a diameter of ⅛ to {fraction (1/16)} inch, makinga water ejection in the form of a sector blade. The edge brushes havebristles 222 and 322 subjected to the ejection of pure water or alongwith NH₄OH or mixture NH₄OH/H₂O of pure water and NH₄OH to prevent thecontaminating particles from being accumulated in the bristles 222 and322 while cleaning the wafer.

[0010] However, such conventional apparatus for cleaning the edge of thewafer employs a plurality of rolls and motors for driving the rolls inorder to clean the edge of the wafer, and therefore, has a complicatedstructure increasing the production cost, and the brushes mechanicallyconstructed may produce physical damages on the wafer by contacting, andmoreover, the wafer may be re-contaminated by the cleaning liquidcontaminated after cleaning the edge of the wafer, lowering the yieldrate of wafers.

DISCLOSURE OF INVENTION

[0011] Hence, it is an object of the present invention to provide anapparatus for dry-cleaning the edge of a wafer through anenvironmentally desirable process using dry ice, which is structurallysimplified reducing the production cost and prevents the wafer frombeing re-contaminated due to the edge cleaning, thus resulting inincrease of the yield rate of wafers.

[0012] This object is achieved by the inventive apparatus for cleaningthe edge of a wafer, which comprises a cleaning agent ejection nozzlebody provided on a side part of a chuck for ejecting a particulatecleaning agent towards the side and the edge portions of the wafer heldand rotated by the chuck, and a nozzle body carriage for moving thenozzle body between rest and cleaning positions.

[0013] The ejection nozzle body is provided with a gas sucker forsucking and treating the gas vaporized from the ejected particulatecleaning agent.

[0014] The particulate cleaning agent preferably consists of dry ice(CO₂) particles.

[0015] Preferably, the nozzle body includes a wafer receiver provided onits front side for receiving an edge portion of the wafer, first nozzlesprovided in the bottom of the wafer receiver for ejecting theparticulate cleaning agent towards the edge of the wafer, second nozzlesprovided in the upper part of the wafer receiver for ejecting theparticulate cleaning agent towards the upper surface of the wafer, andthird nozzles provided below the second nozzle for ejecting theparticulate cleaning agent towards the lower surface of the wafer.

[0016] The nozzles preferably have a diameter of 0.5 to 2 mm.

[0017] The nozzle body carriage may comprise a pneumatic cylinder or astepper motor.

[0018] The particulate cleaning agent is carried by a carrier gas suchas N₂, ejected from the nozzle body towards the edge of the wafer.

[0019] The number of each of kind the first, second and third nozzlesprovided in the nozzle body may be one or more.

[0020] In another aspect of the present invention, the object isachieved by an apparatus for cleaning the edge of a wafer, whichcomprises a cleaning agent storage tank for storing a highly pressurizedcleaning agent; a nozzle body connected through a first line with thecleaning agent storage tank and provided in a side part of a spin chuckfor holding and rotating the wafer so as to eject the cleaning agentconverted into particles, the cleaning agent being depressurized duringpassing the first line; a carrier gas storage tank connected with asecond line connected to the first line for storing a carrier gas tocarry the particulate cleaning agent to the nozzle body; a nozzle bodycarriage for moving the nozzle body between rest and cleaning positions;and a gas sucker for sucking and treating the gas vaporized from thecleaning agent ejected from the nozzle body.

[0021] The cleaning agent consists of CO₂ particles, and the carrier gasof N₂.

[0022] The nozzle body includes a wafer receiver provided on its frontside for receiving an edge portion of the wafer, first nozzles providedin the bottom of the wafer receiver for ejecting the particulatecleaning agent towards the edge of the wafer, second nozzles provided inthe upper part of the wafer receiver for ejecting the particulatecleaning agent towards the upper surface of the wafer, and third nozzlesprovided below the second nozzle for ejecting the particulate cleaningagent towards the lower surface of the wafer.

[0023] The nozzles have a diameter of 0.5 to 2 mm.

[0024] The nozzle body carriage may comprise a pneumatic cylinder or astepper motor.

[0025] The number of each kind of the first, second and third nozzlesprovided in the nozzle body may be one or more.

[0026] The carrier gas storage tank is an N₂ gas bombe for storinghighly pressurized N₂ gas.

[0027] The carrier gas storage tank stores N₂ gas that may be pumped athigh pressure by a pump.

[0028] The line connector connecting the first and second line comprisesa base block for connecting the first and second lines, and orifice andventuri assembly provided between the base block and nozzle body.

BRIEF DESCRIPTION OF DRAWINGS

[0029]FIG. 1 is a schematic diagram of a conventional wafer cleaningapparatus;

[0030]FIGS. 2A to 2C are schematic diagrams for showing the operation ofa conventional apparatus for cleaning the edge of a wafer;

[0031]FIG. 3 is a schematic diagram for showing an apparatus forcleaning the edge of a wafer according to the present invention;

[0032]FIG. 4 is a diagram for illustrating the structure of the nozzlesfor ejecting a cleaning agent towards the upper, lower and side edgeportions of the wafer and a circuit for supplying the nozzles with thecleaning agent in the cleaning apparatus shown in FIG. 3;

[0033]FIG. 5 is an exploded perspective view for illustrating the partconnecting the cleaning agent storage tank and the carrier gas storagetank shown in FIG. 4; and

[0034]FIGS. 6A to 6C are a series of schematic cross sectional views forillustrating the sequential steps of cleaning the edge of the wafer byusing the inventive apparatus for cleaning the edge of a wafer.

BEST MODE FOR CARRYING OUT THE INVENTION

[0035]FIG. 3 is a schematic diagram for cleaning the edge of a wafer bymeans of a dry-cleaning process employing dry ice according to thepresent invention.

[0036] As shown in FIG. 3, the inventive apparatus for cleaning the edgeof a wafer is provided in a side portion of a wafer (W) held by a spinchuck 10 through suction. The apparatus for cleaning the edge of a wafercomprises a nozzle body 1 for ejecting solidified carbon dioxide CO₂,known as dry ice, converted into particles, and a nozzle body carriage 2for moving the nozzle body 1 between rest and cleaning positions. Thenozzle body carriage 2 (hereinafter referred to as pneumatic cylinder)is shown as a pneumatic cylinder by way of illustration, but may consistof a stepper motor. The nozzle body 1 has a lower bracket 5 connected tothe piston 4 of the pneumatic cylinder 2, which is mounted through abracket 6 provided in a side portion of the spin chuck 10 to thecleaning apparatus.

[0037] The nozzle body 1 stands by in the rest position when the spinchuck 10 is holding the wafer (W). When the spin chuck 10 has completedthe operation of holding the wafer (W), the nozzle body 1 is moved bythe forward motion of the pneumatic cylinder 2 to the cleaning positionfor cleaning the edge of the wafer (W), as shown in FIG. 3. The nozzlebody 1 is provided with a wafer receiver 3 for receiving the wafer (W).

[0038] The nozzle body 1, as shown in FIG. 4, includes a plurality ofnozzles 1 a, 1 b, 1 c, of which first nozzles 1 a are provided in thebottom of the wafer receiver 3 in order to eject particulate cleaningagent such as dry ice particles (hereinafter referred to as CO₂particles) towards the edge of the wafer (W) Second nozzles 1 b areprovided in the upper part of the wafer receiver 3 in order to eject CO₂particles towards the upper surface of the wafer (W), and third nozzles1 c positioned below the second nozzles 1 b in order to eject CO₂particles towards the lower surface of the wafer (W). These first,second and third nozzles 1 a, 1 b and 1 c have a diameter of 0.5 to 2mm.

[0039] The edge cleaning of the wafer (W) by using CO₂ is obtained bythe nozzle body 1 that ejects the CO₂ particles produced by the phasetransformation (transformation from gaseous and liquid to solid phase)of CO₂ with pressure and temperature changes towards the wafer (W). Thecleaning principle of the CO₂ ejection depends on firstly impact energy,secondly thermal contraction between the wafer (W) and CO₂ film, thirdlydissolution of contaminants by CO₂, finally sublimable volume expansion,etc. These phenomena are caused by the phase transformation (gaseous andliquid phases) of fine dry ice particles when they impinge upon thesurfaces of the wafer (W). Hence, such actions of CO₂ can eliminate suchcontaminants as polymer that may be generated in the edge and sideportions of the wafer (W) during dry etching. Especially, CO₂ cleaningis more desirable in environmental affinity compared to the conventionalcleaning process, simplifies the process, and results in good cleaningeffect with the inherently excellent dissolution power to organicsubstances of hydrocarbon series.

[0040] The first, second and third nozzles 1 a, 1 b and 1 c of thenozzle body 1 for ejecting particulate CO₂ are connected throughrespective lines 8 a, 8 b and 8 c, as shown in FIG. 4, to a main line16, which in turn is connected through respective lines 16 a and 16 b toa cleaning agent (dry ice) storage tank 11 and carrier gas storage tank17. The carrier gas storage tank 17 stores N₂ gas, which carries the CO₂particles to the nozzle body 1 to clean the edge and side portions ofthe wafer (W). The N₂ gas highly pressurized in the carrier gas storagetank 17 is discharged through the line 16 b connected to the line 16 acommunicating with the cleaning agent storage tank 11 at a lineconnector 12.

[0041]FIG. 5 is a schematic exploded perspective view of the lineconnector connecting the cleaning agent storage tank and carrier gasstorage tank shown in FIG. 4. The line connector 12, as shown in FIG. 5,includes a base block 21, and first and second orifice/venturi blocks 22and 23. The base block 21 serves to connect the line 16 a connected tothe cleaning agent storage tank 11 and the line 16 b connected to thecarrier gas storage tank 17. Provided between the cleaning agent storagetank 11 and the line 16 a is a regulator 24 for regulating the pressureof the cleaning agent stored in the cleaning agent storage tank at ahigh pressure to a relatively low pressure of 100 to 120 psi.Depressurized by the regulator 24, the dry ice from the cleaning agentstorage tank 11 is ejected as the CO₂ particles in the snow state.

[0042] The base block 21 has an internal channel 21 a that includes twoinlet openings 21 b and 21 c respectively connected to the lines 16 aand 16 b, and one outlet opening 21 d connected through the first andsecond orifice/venturi blocks 22 and 23 to the main line 16. The carriergas N₂ from the carrier gas storage tank 17 and the cleaning agentparticulate CO₂ from the cleaning agent storage tank 11 are mixed in theinternal channel 21 a of the base block 21, delivered through the firstand second orifice/venturi blocks 22 and 23 and the line 16 to thenozzle body 1. The first and second orifice/venturi blocks 22 and 23 arerespectively provided with internal orifice/venturi channels 22 a and 23a. Thus, the particulate cleaning agent from the cleaning agent storagetank 11 passes the orifice/venturi blocks 22 and 23, more condensed andsolidified to result in increase of the size of the CO₂ particles.Therefore, the cleaning agent of CO₂ particles is more condensed andsolidified, carried by the carrier gas at a relatively low pressure tothe nozzle body 1.

[0043] The carrier gas storage container may be a gas bombe to storehighly pressurized N₂ gas, or a tank to store a carrier gas at a givenpressure. The carrier gas such as N₂ may be supplied by a pump or thelike to the nozzle body 1 to carry the cleaning agent such as CO₂thereto.

[0044] The nozzles 1 a, 1 b and 1 c of the nozzle body 1 may have anejection angle selected from 1 to 120°, and the number of the first,second or third nozzles 1 a, 1 b or 1 c may be one or more formed alongthe radial direction of the wafer in the nozzle body 1.

[0045] In addition, the nozzle body 1 is provided with a gas sucker 7for sucking and treating the CO₂. gas vaporized due to the CO₂ particlesimpinging upon the surfaces of the wafer (W). The gas sucker 7 sucks anddischarges the CO₂ gas together with all other gases existing around thenozzles 1 a, 1 b and 1 c of the nozzle body and the wafer (w) aftercleaning the edge and side portions of the wafer (W) in order to preventthe wafer (W) from being contaminated by such gases. Moreover, theamount and the ejection pressure of the CO₂ particles ejected throughthe nozzles 1 a, 1 b and 1 c may be properly adjusted as needed.

[0046] In the present embodiment as shown in the attached drawings, thegas sucker 7 is provided concentrically around the first nozzle 1 a,connected through a line 15 to a gas collection tank 14. Thecontaminated residual gas existing around the nozzle body 1 is sucked bya pump 13 provided in the line 15 collected into the gas collection tank14. Such treatment of the residual gas including CO₂ serves to preventthe wafer (W) from being re-contaminated and the atmosphere fromcontamination by it.

[0047] In this case, the first nozzle 1 a is formed of a tube with aninternal diameter of 0.5 to 2 mm as described above, extended throughthe gas sucker 7 from the back side of the nozzle body 1 to the front,and connected to the line 8 a at the back end of the tube. In addition,the second and third nozzles 1 b and 1 c may be perforated with the samediameter respectively in the upper and lower parts of the wafer receiver3 of the nozzle body 1, or formed of respective tubes with the sameinternal diameter as the first nozzle 1 a, connected to the respectivelines 8 b and 8 c.

[0048]FIGS. 6A to 6C illustrates the sequential steps of cleaning theedge of the wafer by using the inventive apparatus.

[0049] Making a forward motion of the pneumatic cylinder 2 to thecleaning position for cleaning the edge of the wafer (W) as shown inFIG. 3, the first and third nozzles 1 a and 1 c eject the particulateCO₂ to clean the side and back edge portions of the wafer (W), as shownin FIG. 6A. The position at which the third nozzle 1 c ejects theparticulate CO₂ is within about 3 mm from the outer side of the wafer(W). Such cleaning of the back edge portions of the wafer (W) is toprevent the front surface of the wafer (W) from being contaminated bythe contaminants that may exist in the back surface. In this case, theline 8 b connected to the second nozzle 1 b has a valve 9 b closed so asto prevent the second nozzle 1 b from ejecting the particulate CO₂.

[0050] Completing the cleaning of the wafer (W) at the relative positionto the particulate CO₂ ejected from the first and third nozzles 1 a and1 c as shown in FIG. 6A over a given time, the nozzle body 1 is movedabout 3 mm backward by retreating the pneumatic cylinder 2 so as toposition the second and third nozzles 1 b and 1 c respectively above andbelow the edge of the wafer (W) as shown in FIG. 6B while working thefirst and third nozzles 1 a and 1 c to continuously eject theparticulate CO₂.

[0051] When the second and third nozzles 1 b and 1 c are positionedrespectively above and below the edge of the wafer (W) by retreating thepneumatic cylinder 2, the valve 9 b provided in the line 8 b connectedto the second nozzle 1 b is opened to eject the particulate CO₂ alongwith the first and third nozzles 1 a and 1 c, as shown in FIG. 6C.Holding this state for a given time, the valves 9 a, 9 b and 9 cprovided in the respective lines 8 a, 8 b and 8 c connected to therespective nozzles 1 a, 1 b and 1 c are closed to stop the ejection ofthe particulate CO₂, and the pneumatic cylinder 2 is completelyretreated to prevent the nozzle body 1 from interfering with the wafer(W).

[0052] When the pneumatic cylinder 2 has completely retreated the nozzlebody 1 from the wafer (W), the edge cleaned wafer (W) is removed by aclamp or the like from the spin chuck 10 for a further processing, andanother fresh wafer (W) is loaded on the spin chuck 10 by means of avacuum force to be treated.

[0053] The inventive apparatus for cleaning the edge of the wafer asdescribed above employs the particulate CO₂, and therefore, may affectthe environment. Namely, the ejection of the particulate CO₂ of very lowtemperature may cause the moisture in the atmosphere to be condensedproducing dew, which may be prevented by a temperature control systemfor controlling the temperature of the local atmosphere around theapparatus.

[0054] Besides, the pneumatic cylinder 2 and the valves 9 a, 9 b and 9 cprovided in the lines 8 a, 8 b and 8 c are controlled by a control unitto control the whole operations of the cleaning apparatus such asholding and removing the wafer (W) by the chuck and cleaning the frontand back surfaces of the wafer (W).

[0055] The inventive apparatus for cleaning the edge of a wafer asdescribed above may also clean both the front surface and edge of thewafer (W) without affecting its front pattern.

[0056] The inventive apparatus for cleaning the edge of a wafer asdescribed above may be relatively simply constructed with low cost, doesnot directly contact the wafer so as to prevent a physical damage of thewafer, and prevents the wafer from being re-contaminated by the edgecleaning, thus resulting in increase of the yield rate of wafers.

[0057] While the present invention has been described in connection witha preferred embodiment accompanied by the drawings attached only by wayof example, it will be apparent to those skilled in the art that it isnot limited to the above embodiment but can be variously altered ormodified without departing the gist of the present invention defined inthe appended claims.

What is claimed is:
 1. An apparatus for cleaning the edge of a wafer,comprising: a cleaning agent ejection nozzle body provided on a sidepart of a chuck for ejecting a particulate cleaning agent towards theside and the edge portions of said wafer held and rotated by said chuck;and a nozzle body carriage for moving said nozzle body between rest andcleaning positions.
 2. An apparatus for cleaning the edge of a wafer asdefined in claim 1, wherein said ejection nozzle body is provided with agas sucker for sucking and treating the gas vaporized from the ejectedparticulate cleaning agent.
 3. An apparatus for cleaning the edge of awafer as defined in claim 1, wherein said particulate cleaning agentconsists of dry ice (CO₂) particles.
 4. An apparatus for cleaning theedge of a wafer as defined in claim 1, wherein said nozzle body includesa wafer receiver provided on its front side for receiving an edgeportion of said wafer, first nozzles provided in the bottom of saidwafer receiver for ejecting said particulate cleaning agent towards theedge of said wafer, second nozzles provided in the upper part of saidwafer receiver for ejecting said particulate cleaning agent towards theupper surface of said wafer, and third nozzles provided below saidsecond nozzle for ejecting said particulate cleaning agent towards thelower surface of said wafer.
 5. An apparatus for cleaning the edge of awafer as defined in claim 4, wherein said nozzles have a diameter of 0.5to 2 mm.
 6. An apparatus for cleaning the edge of a wafer as defined inclaim 1, wherein the number of each kind of said first, second and thirdnozzles provided in said nozzle body is one or more.
 7. An apparatus forcleaning the edge of a wafer as defined in claim 1, wherein said nozzlebody carriage comprises a pneumatic cylinder.
 8. An apparatus forcleaning the edge of a wafer as defined in claim 1, wherein said nozzlebody carriage comprises a stepper motor.
 9. An apparatus for cleaningthe edge of a wafer as defined in claim 1, wherein said particulatecleaning agent is carried by a carrier gas to said nozzle body to beejected from it.
 10. An apparatus for cleaning the edge of a wafer asdefined in claim 9, wherein said carrier gas consists of N₂.
 11. Anapparatus for cleaning the edge of a wafer, comprising: a cleaning agentstorage tank for storing a highly pressurized cleaning agent; a nozzlebody connected through a first line with said cleaning agent storagetank and provided in a side part of a spin chuck for holding androtating said wafer so as to eject said cleaning agent converted intoparticles, said cleaning agent being depressurized during passing saidfirst line; a carrier gas storage tank connected with a second lineconnected to said first line for storing a carrier gas to carry theparticulate cleaning agent to said nozzle body; a nozzle body carriagefor moving said nozzle body between rest and cleaning positions; and agas sucker for sucking and treating the gas vaporized from the cleaningagent ejected from said nozzle body.
 12. An apparatus for cleaning theedge of a wafer as defined in claim 11, wherein said cleaning agentconsists of CO₂ particles, and said carrier gas of N₂.
 13. An apparatusfor cleaning the edge of a wafer as defined in claim 11, wherein saidnozzle body includes a wafer receiver provided on its front side forreceiving an edge portion of said wafer, first nozzles provided in thebottom of said wafer receiver for ejecting said particulate cleaningagent towards the edge of said wafer, second nozzles provided in theupper part of said wafer receiver for ejecting said particulate cleaningagent towards the upper surface of said wafer, and third nozzlesprovided below said second nozzle for ejecting said particulate cleaningagent towards the lower surface of said wafer.
 14. An apparatus forcleaning the edge of a wafer as defined in claim 13, wherein saidnozzles have a diameter of 0.5 to 2 mm.
 15. An apparatus for cleaningthe edge of a wafer as defined in claim 13, wherein the number of eachkind of said first, second and third nozzles provided in said nozzlebody is one or more.
 16. An apparatus for cleaning the edge of a waferas defined in claim 11, wherein said nozzle body carriage comprises apneumatic cylinder.
 17. An apparatus for cleaning the edge of a wafer asdefined in claim 11, wherein said nozzle body carriage comprises astepper motor.
 18. An apparatus for cleaning the edge of a wafer asdefined in claim 11, wherein said carrier gas storage tank is an N₂ gasbombe for storing highly pressurized N₂ gas.
 19. An apparatus forcleaning the edge of a wafer as defined in claim 11, wherein saidcarrier gas storage tank stores N₂ gas pumped at high pressure by apump.
 20. An apparatus for cleaning the edge of a wafer as defined inclaim 11, wherein the line connector connecting said first and secondline comprises a base block for connecting said first and second lines,and orifice and venturi assembly provided between said base block andnozzle body.